Entanglement properties in mixed spin-(1,s) systems

We obtain an exact expression of the negativity for SU(2)-invariant bipartite spin-(1,s) states via the partial time reversal method. Studies of thermal states show that the threshold temperature of entanglement may be arbitrary high when s is sufficient large, indicating that the entanglement is very robust against temperature. Negativities in bilinear-biquadratic system are also considered.